The present invention relates to a head/slider structure adapted to connect slider pads and lead pads through solder balls and more particularly to a head/slider structure suitable for solder ball connection with high-quality by radiation of weaker laser energy.
Recently, magnetic disk drives have come to be used in many electronic devices and the necessity of improving yield in mass production is becoming more and more important. A head gimbal assembly (hereinafter referred to as “HGA”) which supports a slider formed with a magnetic head for data read and write is incorporated in a magnetic disk drive. The HGA comprises a head/slider including a magnetic head and a slider, a flexure constructed so as to permit the head/slider to perform a track follow-up motion while flying over the magnetic head and performing pivotal motions, a load beam which applies a pushing load to the flexure, a mounting plate adaptable to fix the load beam to an actuator assembly, and a lead wire for electric connection between the magnetic head and a circuit board. The construction of the HGA exclusive of the head/slider is designated a suspension assembly.
A slider pad which functions as a relay terminal for connecting the magnetic head to a lead pad formed at an end of the lead wire is formed on an outer side face of the slider. After fabrication of the suspension assembly, the head/slider is fixed to a flexure tongue of the flexure with use of an adhesive. Therefore, it is necessary that the lead pad and the slider pad be connected together electrically after the head/slider is fixed to the flexure tongue.
Soldered surfaces of the lead pad and the slider pad are disposed in a positional relation such that planes including the soldered surfaces intersect perpendicularly to each other (a virtual right angle is formed at an intersecting point when the soldered surfaces of both pads are viewed sideways). FIG. 10 is a diagram illustrating a state where a lead pad and a slider pad are connected together by a solder ball connecting method. In FIG. 10(A) there are shown metallic layers 219a and 219b which constitute a support structure of a flexure, dielectric layers 217a and 217b of polyimide laminated onto the metallic layers 219a and 219b, and a lead wire 221 formed by laminating a copper layer onto the dielectric layer 217b. A head/slider 211 is mounted on the dielectric layer 217a in such a manner that an air bearing surface (hereinafter, referred to as “ABS”) 223 thereof opposed to a magnetic disk faces upward. A magnetic head is embedded into the head/slider 211 so that it can be magnetically coupled with the magnetic disk opposed to the ABS 223. Further, a slider pad 213 for connection between the magnetic head and the lead wire 221 is formed on an end side face of the head/slider 211.
The metallic layer 219a which supports the head/slider 211 is called a flexure tongue and, when the head/slider 211 flies over the surface of the magnetic disk, the metallic layer 219a performs gimbal motions or pivot motions about a dimple which is formed as fulcrum on a load beam (not shown). The lead wire 221 extends toward the front face of the slider pad 213 up to a position such that there remains a space 225 between the position and the head/slider 211. The lead wire 221 is formed with a lead pad 229 at its distal end.
According to the solder ball connecting method, first a spherical solder ball 215 is temporarily fixed so as to come into contact with both the slider pad 213 and lead pad 229 and a laser beam is radiated to the solder ball 215 in the direction of arrow A to melt the solder ball 215. Thereafter, the radiation of the laser beam is stopped, followed by cooling, to form a solder fillet 227 shown in FIG. 10(B) for electric connection between the pads. In the solder ball connecting method, at the time of reflowing the solder ball 215 with use of laser energy, there sometimes occurs a connection defect such as molten solder being attracted strongly to one pad, resulting in the solder fillet 227 being not connected to the other pad, or the area of connection between the solder fillet 227 and the pads being insufficient, or the strength of connection being insufficient, or the occurrence of short-circuit with an adjacent pad. The solder ball reflowing process using a laser beam includes a process of performing both heating and cooling in an extremely short time as is described in Japanese Patent Laid-open No. 10-79105.